Recently, the performance of portable devices has been remarkably increasing. It is desired that power sources of such portable devices are small and have a high capacity. While, the manufacturing of high-capacity batteries becomes difficult as the sizes of the batteries become small.
Patent Literature 1 discloses a battery having a small cylindrical metal can and a sealing member for sealing an opening of the metal can. A winding-type electrode group is accommodated in the metal can. The electrode group includes first and second electrodes, and a separator is interposed between the electrodes. The separator projects on an end surface of the electrode group. The separator thus prevents contact between an electrode and a battery can that have different polarities, and prevents a short circuit between an end of one electrode and an end of the other electrode.